A typical scroll compressor has a fixed scroll which is secured to a frame of the compressor and an orbiting scroll which is operably coupled with the fixed scroll with its rotational axis offset from the center of the fixed scroll. The scrolls have respective spiral laps so as to form a space for compressing refrigerant gas which is sucked in the space by the orbiting scroll as the orbiting scroll is rotated about the fixed scroll.
An Oldham coupling is used to suppress the rotation of the orbiting scroll on its axis so that the orbiting scroll revolves about the fixed scroll. The Oldham coupling, placed between the lower face of the orbiting scroll and the upper face of the frame, has on the upper face thereof a set of two keys and on the lower face thereof another set of two keys. The upper keys are slidably engaged in two key slots formed on the lower face of the orbiting scroll, while the lower keys are each slidably engaged in corresponding ones of two key slots formed on the upper face of the frame. Further, the upper face of the Oldham coupling slidably abuts on the lower face of the orbiting scroll, and the lower face of the Oldham coupling abuts on the upper face of the frame. During a compression operation of the scroll compressor, the Oldham coupling undergoes a rotational motion relative to the orbiting scroll and maintains the revolution of the orbiting scroll around the fixed scroll.
Most orbiting and fixed scrolls are made of an aluminum--silicon (Al--Si) alloy. Al--Si alloys have been widely used for these types of scrolls since they have superb anti-corrosion and abrasion resistance along with low thermal expansion coefficients. Unfortunately, however, the alloys do not have sufficient mechanical strength for the scrolls. In addition, Al--Si alloys have rather poor abrasion resistance when they are in frictional contact with other elements made of iron. This is the case for the orbiting scroll made of an Al--Si alloy in slidable engagement with an iron Oldham coupling.
In view of recent developments in the field of air conditioners and refrigeration apparatuses, there is accordingly a need for an improved Al--Si alloy suitable for a durable orbiting scroll that can work well with the Oldham coupling.
It is therefore an object of the invention to provide a scroll compressor having a orbiting scroll with sufficient mechanical strength against severe conditions imposed on the orbiting scroll during the operation, and having excellent abrasion resistance against the Oldham coupling.